The management, organization and validation of biological information is known as Bioinformatics, that is, “the application of computational techniques to analyse the information associated with biomolecules on a large-scale” [1-2]. Internet is a tremendous source of information that when approached adequately can facilitate the analysis of a particular problem. In this context, many databases are available through Internet, from genes and genomes to protein sequences, metabolic pathways and protein structures (primary to quaternary); and big efforts are being made to integrate and crosslink different sources of information.
In parallel to the availability of this huge amount of data, many computational web resources and tools have been developed to extract a considerable amount of useful information with just a nucleotide or protein sequence. In this lecture, we will focus on these types of resources and how they can be used to obtain from simple information such as the isoelectric point, molecular weight or the extinction coefficient to more complex data such as flexibility, stability, initial crystallization conditions or structural models.